Implantable medical device having flat electrolytic capacitor with porous gas vent within electrolyte fill tube

Abstract

Implantable medical devices (IMDs) and their various components, including flat electrolytic capacitors for same, and methods of making and using same and providing for outgassing of gases released during capacitor charge and discharge cycles are disclosed. A gas vent and liquid electrolyte barrier into the electrolyte fill tube lumen that is used to fill the interior case chamber with electrolyte and then needs to be closed to prevent leakage of electrolyte. The fill port is shaped to comprise a fill port tube having interior and exterior tube ends and a fill port ferrule intermediate the ends of the fill port tube and comprising a fill port ferrule flange extending transversely to and away from the fill port tube. The fill port ferrule is mounted in an opening disposed in one of the case wall and the cover wall with the ferrule flange in sealing engagement therewith to locate the exterior tube end extending outwardly away from the fill port ferrule flange and the interior tube end within the interior case chamber. A microporous plug is injected into and fills the fill port lumen, the plug formed of a microporous material allowing the escape of gas released from the liquid electrolyte during capacitor charging while preventing escape of liquid or vaporized electrolyte.

Description

RELATED APPLICATION[0001]This application claims priority and other benefits from U.S. Provisional Patent Application Ser. No. 60 / 080,564, filed Apr. 3, 1998, entitled FLAT ALUMINUM ELECTROLYTIC CAPACITOR.[0002]This application is a continuation-in-part of U.S. patent application Ser. No. 09 / 103,843 now U.S. Pat. No. 6,157,531 filed Jun. 24, 1998, in the names of Mark K. Breyen et al. and entitled IMPLANTABLE MEDICAL DEVICE HAVING FLAT ELECTROLYTIC CAPACITOR WITH LIQUID ELECTROLYTE FILL TUBE.FIELD OF THE INVENTION[0003]This invention relates to implantable medical devices (IMDs) and their various components, including flat electrolytic capacitors for same, and methods of making and using same and providing for outgassing of gases released during capacitor charge and discharge cycles.BACKGROUND OF THE INVENTION[0004]As described in the above-referenced parent application Ser. No. 09 / 103,843, and the provisional application that it claims priority from, a wide variety of IMDs are know...

AI Technical Summary

Benefits of technology

The present invention is about improving venting in flat electrolytic capacitors used in IMDs. The invention solves problems by incorporating a gas vent and liquid electrolyte barrier into the electrolyte fill tube lumen that needs to be closed to prevent leakage of electrolyte. A microporous plug is injected into the fill port lumen to allow gas released from the liquid electrolyte during capacitor charging while preventing escape of liquid or vaporized electrolyte. The plug solidifies and adheres to the interior case chamber to inhibit expulsion of the plug outward from the tube lumen under gas pressure. The technical effects of the invention include improved venting, prevention of electrolyte leakage, and protection of the capacitor from damage during charging.

Problems solved by technology

Earlier developed automatic implantable defibrillators (AIDs) did not have cardioversion or pacing capabilities.

The battery(s) and high voltage capacitor(s) used to provide and accumulate the energy required for the cardioversion / defibrillation shocks have historically been relatively bulky and expensive.

At the same time, reliability of the capacitors cannot be compromised.

Consequently, these and other components in a capacitor and the desired capacitance limit the extent to which its physical dimensions may be reduced.

The cylindrical shape and paper core of commercial photoflash capacitors limits the volumetric packaging efficiency and thickness of an ICD IPG housing made using same.

However, leakage can occur if such batteries are not kept upright.

Severe hydrogen accumulation can cause the capacitor case walls to swell outward and conceivably could cause the capacitor case to rupture at a laser weld seam or feedthrough.

These approaches may be suitable in environments where the electrolyte can cause no harm and the capacitor can be readily replaced, but are inappropriate in the close confines of an IPG housing where the capacitor cannot be replaced and the electrolyte could harm other components.

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